Embedment of medical lead coil electrodes

ABSTRACT

In some examples, a coil electrode assembly includes a coil electrode including a plurality of windings and extending from an electrode proximal end to an electrode distal end, the coil electrode defining an electrode lumen from the electrode proximal end to the electrode distal end. The coil electrode assembly further includes an insulative tube extending within the lumen of the coil electrode such that the coil electrode extends along an outer surface of the insulative tube. The coil electrode is partially embedded within the insulative tube when the insulative tube is in an expanded state to maintain a spacing between the windings.

FIELD

This disclosure is generally related to implantable medical devices.

BACKGROUND

Implantable medical devices may be used to monitor a variety ofconditions of patients and/or to deliver a variety of therapies topatients. Some implantable medical devices include electrodes to senseelectrical signals and/or deliver electrical therapies. Some implantablemedical devices include elongated leads to position the electrodesproximate to target tissue for sensing or therapy delivery. For example,an implantable medical device may deliver anti-tachyarrhythmia (e.g.,defibrillation) shocks via one or more coil electrodes that are part ofone or more leads and are located within or proximate to the heart.

SUMMARY

The techniques of this disclosure generally relate to assemblingimplantable medical leads including coil electrodes and, moreparticularly, to securing the windings of a coil electrode, e.g.,preserving intra-winding spacing, by an “inside-out” approach. In someexisting implantable medical leads, coil electrodes are secured using anadhesive applied from the outside of the coil electrode. In contrast,the techniques of the present disclosure secure the coil electrode usingan insulative tube disposed within a lumen defined by the coilelectrode, which may increase the surface area of the coil electrodeavailable for blood/tissue contact to interact with relative to theexisting implantable medical leads.

The insulative tube within the lumen is transitioned to an expandedstate to make contact with the coil electrode, e.g., such that the coilelectrode is partially embedded within the insulative tube, and thussecure the spacing between the windings. The expansion of the tube maybe done through the application of heat and/or air pressure to theinside of the tube. In some examples, prior to expanding the insulativetube, transition rings are connected at the ends of the coil electrodeand the tube to maintain them in place relative to one another duringexpansion of the tube.

In some examples, the coil electrode assembly may be constructed as asubassembly for the implantable medical leads. Making the implantablemedical lead using such a subassembly process can help reduce waste,because if one subassembly part needs to be scrapped, the remainingportion of the lead does not need to be scrapped as well. Examples inwhich the coil electrode assembly includes one or more conductivetransition rings may also facilitate electrical connection of the coilelectrode to a conductor of the implantable medical lead via thetransition ring.

In one example, the present disclosure provides an implantable medicallead configured to be coupled to an implantable medical device, theimplantable medical lead comprising a coil electrode assembly. The coilelectrode assembly comprises a coil electrode extending from anelectrode proximal end to an electrode distal end, the coil electrodedefining an electrode lumen from the electrode proximal end to theelectrode distal end, and the coil electrode comprising a plurality ofwindings. The coil electrode assembly further comprises an insulativetube extending from a tube proximal end to a tube distal end, theinsulative tube extending within the electrode lumen such that the coilelectrode extends along an outer surface of the insulative tube, thecoil electrode partially embedded within the insulative tube when theinsulative tube is in an expanded state to maintain a spacing betweenthe windings. The coil electrode assembly further comprises a firsttransition ring at the electrode distal end and the tube distal end,wherein a portion of the first transition ring is within the electrodelumen, wherein the first transition ring defines a first transition ringlumen, and wherein a distal portion of the insulative tube including thetube distal end is within the first transition ring lumen. The coilelectrode assembly further comprises a second transition ring at theelectrode proximal end and the tube proximal end, wherein a portion ofthe second transition ring is within the electrode lumen, wherein thesecond transition ring defines a second transition ring lumen, andwherein a proximal portion of the insulative tube including the tubeproximal end is within the second transition ring lumen.

In another example, the disclosure provides a system comprising animplantable medical device configured to generate an antitachyarrhythmiashock, and an implantable medical lead extending from a lead proximalend to a lead distal end, the lead proximal end configured to be coupledto the implantable medical device, the implantable medical leadcomprising a coil electrode assembly between the lead proximal end andthe lead distal end. The coil electrode assembly comprises a coilelectrode extending from an electrode proximal end to an electrodedistal end, the coil electrode defining an electrode lumen from theelectrode proximal end to the electrode distal end, and the coilelectrode comprising a plurality of windings, wherein the coil electrodeis configured to deliver the antitachyarrhythmia shock. The coilelectrode assembly further comprises an insulative tube extending from atube proximal end to a tube distal end, the insulative tube extendingwithin the electrode lumen such that the coil electrode extends along anouter surface of the insulative tube, the coil electrode partiallyembedded within the insulative tube when the insulative tube is in anexpanded state to maintain a spacing between the windings. The coilelectrode assembly further comprises a first transition ring at theelectrode distal end and the tube distal end, wherein a portion of thefirst transition ring is within the electrode lumen, wherein the firsttransition ring defines a first transition ring lumen, and wherein adistal portion of the insulative tube including the tube distal end iswithin the first transition ring lumen. The coil electrode assemblyfurther comprises a second transition ring at the electrode proximal endand the tube proximal end, wherein a portion of the second transitionring is within the electrode lumen, wherein the second transition ringdefines a second transition ring lumen, and wherein a proximal portionof the insulative tube including the tube proximal end is within thesecond transition ring lumen.

In another example, the disclosure provides a coil electrode assemblyfor an implantable medical lead configured to be coupled to animplantable medical device. The coil electrode assembly comprises a coilelectrode extending from an electrode proximal end to an electrodedistal end, the coil electrode defining an electrode lumen from theelectrode proximal end to the electrode distal end, and the coilelectrode comprising a plurality of windings. The coil electrodeassembly further comprises an insulative tube extending from a tubeproximal end to a tube distal end, the insulative tube extending withinthe electrode lumen such that the coil electrode extends along an outersurface of the insulative tube, the coil electrode partially embeddedwithin the insulative tube when the insulative tube is in an expandedstate to maintain a spacing between the windings. The coil electrodeassembly further comprises a first transition ring at the electrodedistal end and the tube distal end, wherein a portion of the firsttransition ring is within the electrode lumen, wherein the firsttransition ring defines a first transition ring lumen, and wherein adistal portion of the insulative tube including the tube distal end iswithin the first transition ring lumen. The coil electrode assemblyfurther comprises a second transition ring at the electrode proximal endand the tube proximal end, wherein a portion of the second transitionring is within the electrode lumen, wherein the second transition ringdefines a second transition ring lumen, and wherein a proximal portionof the insulative tube including the tube proximal end is within thesecond transition ring lumen.

In another example, a method comprises inserting an insulative tubewithin an electrode lumen defined by a coil electrode of a coilelectrode assembly such that the coil electrode extends along an outersurface of the insulative tube, the insulative tube extending from atube proximal end to a tube distal end and the coil electrode extendingfrom an electrode proximal end to an electrode distal end, and the coilelectrode comprising a plurality of windings. The method furthercomprises connecting a first transition ring to the coil electrode atthe electrode distal end and to the insulative tube at the tube distalend, and connecting a second transition ring to the coil electrode atthe electrode proximal end and to the insulative tube at the tubeproximal end. The method further comprises applying at least one of heatand gas pressure to the insulative tube to transition the insulativetube from a non-expanded state to an expanded state such that the coilelectrode is partially embedded within the insulative tube and a spacingbetween the windings is maintained.

This summary is intended to provide an overview of the subject matterdescribed in this disclosure. It is not intended to provide an exclusiveor exhaustive explanation of the methods and systems described in detailwithin the accompanying drawings and description below. The details ofone or more aspects of the disclosure are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages of the techniques described in this disclosure will beapparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a conceptual diagram illustrating an example medical devicesystem including an implantable medical device coupled to one or morecoil electrodes on one or more implantable medical leads.

FIG. 2 is a cross-sectional diagram illustrating an example coilelectrode assembly.

FIG. 3 is a cross-sectional diagram further illustrating a view ofregion A of a first end portion of the example coil electrode assemblyof FIG. 2.

FIG. 4 is a cross-sectional diagram further illustrating a view ofregion B of a second end portion of the example coil electrode assemblyof FIG. 2.

FIG. 5 is a conceptual diagram illustrating an exploded view of theexample coil electrode assembly of FIG. 2.

FIGS. 6A and 6B are cross-sectional diagrams illustrating apre-expansion state and a post-expansion state, respectively, of aregion of another example coil electrode assembly similar to region A ofthe example coil electrode assembly of FIG. 2.

FIGS. 7A and 7B are cross-sectional diagrams illustrating apre-expansion state and a post-expansion state, respectively, of anotherregion of the other example coil electrode assembly similar to region Bof the example coil electrode assembly of FIG. 2.

FIG. 8 is a flow diagram of an example technique for manufacturing acoil electrode assembly to be attached to an implantable medical lead.

DETAILED DESCRIPTION

Electrodes used to deliver relatively higher-energy (e.g., compared tocardiac pacing) anti-tachyarrhythmia (e.g., defibrillation) shocks cantake the form of a wound coil with the outside surface exposed to theblood or other bodily fluid. The windings of these coils are typicallysecured in their axial position with respect to the underlying lead bodytube and each other (e.g., to avoid filar dislocation, fracture, orfibrosis tissue ingrowth) through depositing silicone adhesive orsilicone rubber in an outside-in direction to cover the wound coil andthe space between the coils. Due to this deposition of the siliconeadhesive or silicone rubber, an exterior surface of wound coil,including the spaces between the electrodes, can be fully or partiallycovered with a thin coating.

While the thin coating can lock the wound coils in place, preventingmovement of the defibrillation coil electrode, the coating maypotentially reduce the performance of the coil electrode due to reducedavailable surface area of the coil electrode. In some examples, in orderto counteract the reduction of available surface area of the coilelectrode, the excess adhesive is removed from the outer surface of thecoil. However, removing the adhesive requires relatively skilled laborand adds a step to the process of making the implantable medical leadincluding the coil electrode. Also, using conventional lead assemblytechniques, errors in the application of the adhesive or the removal ofthe thin coating may lead to scrapping the entire implantable medicallead.

A coil electrode assembly according to this disclosure includes aninsulative tube within a lumen defined by the coil electrode, and theinsulative tube is transitioned to an expanded state to partially embedthe coil electrode to secure the coil windings in place via aninside-out approach. In this manner, the coil electrode assemblydescribed herein may have increased outer surface area for delivery ofanti-tachyarrhythmia shocks. Increasing the available surface areas ofthe coil can increase the effectiveness of the shock delivered, e.g.,during ventricular tachycardia (VT) and ventricular fibrillation (VF).Additionally, manufacturing an implantable medical lead including a coilelectrode assembly, as described herein, can reduce operator variabilityand provide cost savings by creating subassemblies that are to beassembled together to create the final product. For example, if the coilelectrode assembly is not assembled correctly, only the coil electrodeassembly needs to be scrapped.

FIG. 1 is a conceptual diagram illustrating an example medical devicesystem 10 including an implantable medical device (IMD) 16 coupled toone or more coil electrodes on one or more implantable medical leads. Inthe example of FIG. 1, IMD 16 is coupled to leads 18 and 22. IMD 16 maybe, for example, an implantable pacemaker, cardioverter, and/ordefibrillator that provides electrical signals to heart 12 viaelectrodes coupled to one or more of leads 18 and 22.

In the example of FIG. 1, leads 18 and 22 extend into the heart 12 tosense electrical activity of a heart 12 and/or deliver electricaltherapy to heart 12. Right ventricular (RV) lead 18 extends through oneor more veins (not shown), the superior vena cava (not shown), and rightatrium 26, and into right ventricle 28. Right atrial (RA) lead 22extends through one or more veins and the vena cava, and into the rightatrium 26 of heart 12. Although example system 10 includes intravascularleads and intracardiac electrodes, extravascular leads includingextravascular coil electrodes may include coil electrode assembliesaccording to the techniques of this disclosure.

IMD 16 may sense electrical signals attendant to the depolarization andrepolarization of heart 12 via electrodes coupled to at least one of theleads 18 and 22. In some examples, IMD 16 provides pacing pulses toheart 12 based on the electrical signals sensed within heart 12. Theconfigurations of electrodes used by IMD 16 for sensing and pacing maybe unipolar or bipolar. IMD 16 may detect arrhythmia of heart 12, suchas tachycardia or fibrillation of the atria (including right atrium 26)and/or the ventricles (including right ventricle 28), and may alsoprovide anti-tachyarrhythmia shocks, e.g., defibrillation and/orcardioversion shocks, via electrodes located on at least one of theleads 18 and 22. In some examples, IMD 16 may be programmed to deliver aprogression of therapies, e.g., pulses with increasing energy levels,until a fibrillation of heart 12 is stopped. IMD 16 may detectfibrillation employing one or more fibrillation detection techniquesknown in the art.

As shown in FIG. 1, the proximal ends of leads 18 and 22 are connectedto a connector block 34 of IMD 16 to electrically couple the electrodeson the leads to circuitry within the housing 60 of IMD 16. In someexamples, proximal ends of leads 18 and 22 may include electricalcontacts that electrically couple to respective electrical contactswithin connector block 34 of IMD 16. Each of the leads 18 and 22includes an elongated insulative lead body, which may carry a number ofconductors, e.g., a conductor for each electrode on the lead, each ofwhich may be connected to a respective contact at the proximal end ofthe lead. Bipolar electrodes 40 and 42 are located adjacent to a distalend of lead 18 in right ventricle 28. In addition, bipolar electrodes 48and 50 are located adjacent to a distal end of lead 22 in right atrium26.

Electrodes 40 and 48 may take the form of ring electrodes, andelectrodes 42 and 50 may take the form of helix tip electrodes mounted,e.g., with a fixed screw, within insulative electrode heads 52 and 56,respectively. Some helix tip electrodes can include a mechanism for anextendable/retractable helix. In other examples, one or more ofelectrodes 42 and 50 may take the form of small circular electrodes atthe tip of a tined lead or other fixation element. Leads 18 and 22 alsoinclude elongated electrodes 62 and 66, respectively, each of which maytake the form of a coil. Each of the electrodes 40, 42, 48, 50, 62 and66 may be electrically coupled to a respective one of the conductorswithin the lead body of its associated lead 18 and 22, and therebycoupled to respective ones of the electrical contacts on the proximalend of leads 18 and 22.

In the example of FIG. 1, IMD 16 includes a housing electrode 58, whichmay be formed integrally with an outer surface of hermetically-sealedhousing 60 of IMD 16, or otherwise coupled to housing 60. In someexamples, housing electrode 58 is defined by an uninsulated portion ofan outward facing portion of housing 60 of IMD 16. Other divisionbetween insulated and uninsulated portions of housing 60 may be employedto define two or more housing electrodes. In some examples, housingelectrode 58 comprises substantially all of housing 60.

IMD 16 may sense electrical signals attendant to the depolarization andrepolarization of heart 12 via electrodes 40, 42, 48, 50, 62, and 66.The electrical signals are conducted to IMD 16 from the electrodes viathe respective leads 18 and 22. IMD 16 may sense such electrical signalsvia any bipolar combination of electrodes 40, 42, 48, 50, 62, and 66.Furthermore, any of the electrodes 40, 42, 48, 50, 62, and 66 may beused for unipolar sensing in combination with housing electrode 58. Thecombination of electrodes used for sensing may be referred to as asensing configuration or electrode vector.

In some examples, IMD 16 delivers pacing pulses via bipolar combinationsof electrodes 40, 42, 48 and 50 to produce depolarization of cardiactissue of heart 12. In some examples, IMD 16 delivers pacing pulses viaany of electrodes 40, 42, 48 and 50 in combination with housingelectrode 58 in a unipolar configuration. Furthermore, IMD 16 maydeliver antitachyarrhythmia shocks, e.g., defibrillation shocks, toheart 12 via any combination of elongated electrodes 62 and 66, andhousing electrode 58. IMD 16 may also use electrodes 58, 62, and 66 todeliver cardioversion shocks to heart 12. Electrodes 62 and 66 may befabricated from any suitable electrically conductive material, such as,but not limited to, platinum, platinum alloy or other materials known tobe usable in implantable defibrillation electrodes.

The configuration of system 10 illustrated in FIG. 1 is merely oneexample. In other examples, a system may include extravascular leads andelectrodes instead of or in addition to the transvenous leads 18 and 22illustrated in FIG. 1. Further, IMD 16 need not be implanted within thepatient. In examples in which IMD 16 is not implanted in the patient,IMD 16 may sense electrical signals and/or deliver antitachyarrhythmiashocks and other therapies to heart 12 via percutaneous leads thatextend through the skin of a patient to a variety of positions within oroutside of heart 12.

FIG. 2 is a cross-sectional diagram that illustrates an example coilelectrode assembly 100. FIG. 3 is a cross-sectional diagram that furtherillustrates a view of a first end portion 134 (region A from FIG. 2) ofcoil electrode assembly 100. FIG. 4 is a cross-sectional diagram thatfurther illustrates a view of a second end portion 136 (region B fromFIG. 2) of coil electrode assembly 100. FIG. 5 is a conceptual diagramillustrating an exploded view of the example coil electrode assembly ofFIG. 2.

Coil electrode assembly 100 includes a coil electrode 112, an insulativetube 122, a first transition ring 124, and a second transition ring 126.When assembled as shown in FIG. 2, lumen respectively defined by each ofinsulative tube 122, first transition ring 124 and second transitionring 126 collectively define a lumen 102 of coil electrode assembly 100.Either or both of elongated electrodes 62 and 66 on leads 18 and 22,respectively, may be assembled according to the techniques describedherein with respect to coil electrode assembly 100. In general, coilelectrode assembly 100 may be included in an implantable medical lead ata desired position between a proximal end and a distal end of the lead.

Although inclusion on an implantable medical lead is described herein asan example, coil electrode assembly 100 can be used with other medicaldevices and/or therapies. In general, coil electrode assembly 100 can beused in any medical device or non-medical device.

In the example of FIG. 2, coil electrode 112 includes a plurality ofwindings 114 that extend from a coil electrode distal end 118 to a coilelectrode proximal end 120. Windings 114 define a coil lumen 116 from adistal end 118 to a proximal end 120 of coil electrode 112. As shown inFIG. 5, insulative tube 122 extends from a tube proximal end 138 to atube distal end 139. Insulative tube 122 extends within coil lumen 116,e.g., from the electrode distal end 118 to the electrode proximal end120, such that coil electrode 112 extends along an outer surface 141(FIG. 5) of insulative tube 122. When insulative tube 122 is in anexpanded state to maintain a spacing 168 (as shown in FIG. 3) betweenwindings 114, coil electrode 112 is partially embedded within insulativetube 122.

Insulative tube 122 may include a polymer including polyurethane and/orsilicone. Inclusion of a polyurethane may provide desirable mechanicalproperties, such as relatively increased tensile and tear strength in atleast the expanded state, compared to a similar thickness tube made fromother materials. In some examples, the polymer or other material ofinsulative tube 122 may have a durometer hardness of at least 50 ShoreD, such as approximately 55 Shore D.

First transition ring 124 is connected to coil electrode 112 at coilelectrode distal end 118, and second transition ring 126 is connected tocoil electrode 112 at coil electrode proximal end 120. In some examples,a first transition ring junction 130 defines a surface for the coilelectrode to abut for the connection between first transition ring 124and coil electrode 112, and a second transition ring junction 132defines a surface for the coil electrode to abut for the connectionbetween second transition ring 126 and coil electrode 112. Theconnection can be provided by multiple methods including welding,crimping, and staking, as examples. In some examples, each of firsttransition ring junction 130 and second transition ring junction 132 canwithstand a tensile pull force of at least 1.0 pound.

First transition ring 124 defines an inner lumen 125 (FIGS. 3 and 5) andsecond transition ring 126 defines an inner lumen 127 (FIGS. 4 and 5).Insulative tube 122 defines an insulative tube lumen 123 (FIGS. 2 and5). At least a portion of first transition ring 124 and secondtransition ring 126 are disposed within coil lumen 116, and in someexamples between coil electrode 112 and an outer surface, e.g., outersurface 141 (FIG. 5), of insulative tube 122. Inner lumen 125 of firsttransition ring 124, insulative tube lumen 123, and inner lumen 127 ofsecond transition ring 126 form lumen 102 of coil electrode assembly100.

First transition ring 124 is connected to insulative tube 122 at tubedistal end 139, and second transition ring 126 is connected toinsulative tube 122 at tube proximal end 138. In some examples, a distalrecess 166 (FIGS. 2, 3 and 5) is formed in a distal portion 140 (FIGS. 3and 5) of insulative tube 122, and a proximal recess 186 (FIGS. 2, 4 and5) in a proximal portion 142 (FIGS. 4 and 5) of insulative tube 122.Portions of first transition ring 124 and second transition ring 126extending medially from junctions 130 and 132, respectively, can receivethe portions of insulative tube 122 defining the respective one of therecesses 166 and 186. Distal recess 166 can help provide a secure fitbetween first transition ring 124 and insulative tube 122. Distal recess166 and proximal recess 186 of insulative tube 122 can be reciprocallyshaped to transition rings 124 and 126 so there is a substantiallysmooth transition from insulative tube 122 to transition rings 124 and126. As illustrated in FIGS. 2-4, the combined thickness of insulativetube 122 at recesses 166 and 186 and the mated portions of transitionrings 124 and 126 may define a substantially similar thickness to thethickness of the remainder of insulative tube 122.

In some examples, insulative tube 122 need not include recesses 166 and186. Nevertheless, in such examples, distal portion 140 of insulativetube 122 including distal tube end 139 may be received within distalring lumen 125, and proximal portion 142 of insulative tube 122including proximal tube end 138 may be received within proximal ringlumen 127. An example of a coil electrode assembly in which aninsulative tube does not include recesses at the distal and proximalportions is described with respect to FIGS. 6A-7B.

First transition ring 124 and second transition ring 126 may be made ofa conductive material. In some examples, coil electrode assembly 100 canhave one or more electrical conductors. A first electrical conductor 144a of an implantable medical lead (e.g., lead 18 or 22) may beelectrically coupled to coil electrode 112 via at least one of the firsttransition ring 124 and second transition ring 126. In the exampleillustrated by FIG. 4, first electrical conductor 144 a is coupled tosecond transition ring 126. First electrical conductor 144 a may connectcoil electrode 112, via transition ring 126 to the proximal end of theimplantable medical lead.

In some examples, as shown in FIG. 2, a second conductors 144 b mayconnect one or more electrodes distal of coil electrode assembly 100 tothe proximal end of the implantable medical lead and, thus to the IMD(conductors 144 a and 144 b collectively as conductors 144). Forexample, with respect to the example of FIG. 2, second conductor 144 bmay extend through lumen 102 to connect electrodes 40 and 42 (or 48 and50) to IMD 16 through coil electrode assembly 100 in which coilelectrode 112 corresponds to electrode 62 and 66 (shown in FIG. 1).

As illustrated in FIG. 3, first transition ring 124 may include aproximal end 162 and a distal end 164. The proximal and distal sidesextend from respective ends, 162 and 164, to an increased diametershoulder 150. The proximal and distal sides of shoulder 150 can havedifferent shapes and sizes. For example, proximal side of shoulder 150can include a curved corner, and distal side of shoulder 150 can includea 90-degree (90°) corner. Proximal side of shoulder 150 provides firsttransition ring junction 130 which may include a surface for coilelectrode 112 to engage. In some examples, coil electrode 112 may bewelded to first transition ring 124 at proximal side of shoulder 150.Distal side of shoulder 150 provides a surface for coil electrodeassembly 100 to connect with a remainder of a lead body of animplantable medical lead.

FIG. 4 is a conceptual diagram that illustrates an example proximalportion of coil electrode assembly 100 including second transition ring126. Second transition ring 126 may be similar to first transition ring124. In the illustrated example, second transition ring 126, with aproximal end 180 and a distal end 182, includes two increased diameterportions, defining a first shoulder 170 and a second shoulder 172. Adistal side of shoulder 170 can include a curved corner, and proximalside of shoulder 170 can include an approximately 90-degree (90°)corner. Distal side of shoulder 170 provides second transition ringjunction 132 which may include a surface for coil electrode 112 toengage. In some examples, coil electrode 112 may be welded to secondtransition ring 126 at proximal side of shoulder 170. In some examples,second shoulder 172 can provide a transition to the body of theimplantable medical lead. Similar, to first transition ring 124, secondtransition ring 126 has holes 176A, 176B, 184A, 184B and grooves 178 and188 to increase structural integrity of the joint by, e.g., addingadditional locations/geometries for mechanical fixation of components.Similar to recess 166 at distal end of insulative tube 122, proximal endof insulative tube 122 also has a proximal recess 186 and functions toprovide a connection between insulative tube 122 and second transitionring 126.

First transition ring 124 is connected to a distal portion 140 (FIG. 3)of insulative tube 122, and second transition ring 126 is connected toproximal portion 142 (FIG. 4) of insulative tube 122. Adhesive 146 isdisposed on distal portion 140 of insulative tube 122 and proximalportion 142 of insulative tube 122, e.g., outer surface 141 ofinsulative tube 122 at these portions. Adhesive 146 connects firsttransition ring 124 to distal portion 140 of insulative tube 122 andsecond transition ring 126 to proximal portion 142 of insulative tube122.

Adhesive 146 can be disposed in one location or multiple locations. Insome examples, adhesive 146 is disposed only on two locations ofinsulative tube 122. The first location for adhesive 146 is locatedbetween a surface of first transition ring 124 and the distal portion140 of insulative tube 122. The second location for adhesive 146 isbetween a surface of second transition ring 126 and the proximal portion142 of insulative tube 122. In each location, adhesive 146 may beapplied continuously or discontinuously as beads, a spray, parallellines, or various patterns. For example, adhesive 146 can be applied ina continuous coating to the distal portion 140 of insulative tube 122and applied in a discontinuous coating to the proximal portion 142 ofinsulative tube 122.

The amount of adhesive 146 applied to coil electrode assembly 100 mayvary over a wide range. The composition of adhesive 146 can vary as welland can include silicone adhesive. In some examples, adhesive 146 can bea mixture of heptane and adhesive. Different compositions of adhesive146 can be applied to different parts of insulative tube 122. Forexample, some portions of coil electrode assembly 100 may include astronger adhesive 146 than other parts. In some examples, the connectionof transition rings 124 and 126 to tube 122 may be by a variety of meansin addition to or instead of adhesive 146.

Some areas of coil electrode assembly 100 can be free of adhesive 146.For example, an outer surface of coil electrode 112 may be substantiallyfree of adhesive 146. At least part of first transition ring 124, afirst area 145, can be free of adhesive 146. Similarly, at least part ofsecond transition ring 126, a second area 147, can be free of adhesive146. Both first transition ring 124 and second transition ring 126 caninclude multiple areas free of adhesive 146. By reducing the amount ofadhesive 146 on the outer surface of coil electrode 112, the surfacearea of coil electrode 112 that is available to interact with thepatient is increased, thereby potentially increasing the effectivenessof an implantable medical lead including coil electrode assembly 100.

Grooves 154 and holes 156A and 156B (collectively “holes 156”) securefirst transition ring 124 to insulative tube 122. Grooves 154 canfacilitate connection with the use of adhesive. Holes 156 can also beused for inspection and verification. For example, holes 156 can be usedto visually ensure insulative tube 122 is properly positioned in firsttransition ring 124. Holes 156A and 156B are on opposite sides of firsttransition ring 124. Holes 156 extend from outer surface of firsttransition ring 124 to inner lumen 125 of first transition ring 124. Insome examples, instead of two holes 156A and 156B, there could be onehole or more than two holes 156. In some examples, multiple holes 156could be placed circumferentially around first transition ring 124.Multiple holes 156 could be evenly or irregularly spaced. There couldalso be multiple holes 156 spaced longitudinally along first transitionring 124, instead of or in addition to holes 156 spacedcircumferentially.

Grooves 154 can extend circumferentially around first transition ring124. In some examples, grooves 154 may not extend completelycircumferentially around first transition ring 124. For example, grooves154 may extend only partially around the circumference of firsttransition ring 124. In addition, the angle of grooves 154 to thelongitudinal axis of first transition ring 124 may vary. For example,grooves 154 may extend perpendicular or at an angle to a longitudinalaxis of first transition ring 124.

Grooves 158 and holes 160A and 160B (collectively “holes 160”) may bethe same or substantially similar or different than grooves 154 andholes 156A and 156B. In some examples, grooves 154 and 158 may besubstantially similar, and holes 156 may be different than holes 160, orvice versa. Grooves 158 and holes 160 provide connection means for firsttransition ring 124 and coil electrode assembly 100, respectively, toconnect with other components and/or assemblies of the implantablemedical lead. Grooves 158 can be used with adhesive to provide aconnection between first transition ring 124 and a lead body. In someexamples, grooves 158 can be used to promote an adhesive connection toother components, e.g., by increasing bond strength. Other connectionmeans besides or in addition to grooves 154, 158 and holes 156, 160could be used as well. Holes 156 and 160 can enable second conductor 144b to make an electrical connection from inner lumen 125 of firsttransition ring 124 to the exterior of first transition ring 124.Similar, to first transition ring 124, second transition ring 126 (FIG.4) has holes 176A, 176B, 184A, 184B and grooves 178 and 188, which mayprovide substantially similar functionality to holes 156 and 160 andgrooves 154 and 158 of first transition ring 124 (FIG. 3). In someexamples, transition rings 124 and 126 can use holes 156, 160, 176, and184 to promote adhesion to an attached component and provide aninspection/verification feature. In some examples, transition rings 124and 126 may be free of holes 160 and 176.

FIGS. 6A and 6B are cross-sectional diagrams illustrating apre-expansion state and a post-expansion state, respectively, of aregion of another example coil electrode assembly similar to region A ofthe example coil electrode assembly of FIG. 2. First end portion 200 ofFIGS. 6A and 6B is similar to first end portion 134, except for thedifferences described herein. For example, like first end portion 134,first end portion 200 includes a first transition ring 210, a coilelectrode 224, and an insulative tube 226. First transition ring 210 isconnected to a distal portion of a lead body 202. A conductor 208extends through the middle of first end portion 200. A first insulatorlayer 206 and a second insulator layer 204 surround conductor 208. Insome examples, first insulator layer 206 is a cable jacket, which canhelp protect conductor 208 from abrasion during or after assembly. Insome examples, second insulator layer 204 is a tubing and can be madefrom any suitable insulative layer, such as, but not limited to, apolymer including polyurethane, silicone, or other materials known to beusable for insulative layers for conductors in medical applications.

In some examples, cable conductor 208 can be used as a pacing conductor,e.g., a cable conductor such as a stranded cable, and can besubstantially similar to second conductor 144 b. First transition ring210 can be substantially similar to first transition ring 124. Firsttransition ring 210 has grooves 216 and 222 and holes 212, 214, 218, and220. Insulative tube 226 can be expanded so coil electrode 224 can bepartially embedded within insulative tube 226, e.g., as shown in FIG.6B, to maintain a spacing between the windings of coil electrode.

Unlike insulative tube 122 of FIG. 3, insulative tube 226 does notinclude a recess similar to distal recess 166 of first end portion 134.Instead, insulative tube 226 has a substantially uniform wall thicknessalong its entire length. Insulative tube 226 may require simplermanufacturing, e.g., fewer steps, then insulative tube 122 that includesrecess 166. FIG. 6B shows insulative tube 226 in an expanded state suchthat coil electrode 224 is partially embedded within the post-expansioninsulative tube 226.

FIGS. 7A and 7B are cross-sectional diagrams illustrating apre-expansion state and a post-expansion state, respectively, of aregion of the other example coil electrode assembly similar to region Bof the example coil electrode assembly of FIG. 2. A second end portion240 of FIGS. 7A and 7B is similar to second end portion 136 of FIG. 2,except for the differences described herein. For example, second endportion 240 includes insulative tube 226, coil electrode 224, secondtransition ring 250, a coil conductor 260, and a lead body 272.Conductor 208 is surrounded by a first insulator layer 206 and a secondinsulator layer 204.

In some examples, second transition ring 250 differs from secondtransition ring 126 of FIG. 2. For example, second transition ring 250lacks a second shoulder. Further, grooves 258 can vary in size along alongitudinal length of second transition ring 250. For examples, grooves258 on one portion of second transition ring 250 can be sized to promotean adhesive connection between second transition ring 250 and lead body272. On a second, different portion of second transition ring 250grooves 258 can be sized to provide connection between first transitionring 250 and coil conductor 260.

In a pre-expanded state, an inner diameter of an insulative tube may besubstantially constant from the tube distal end to the tube proximalend, e.g., as illustrated with respect to insulative tube 226 in FIGS.6A and 7A. In the expanded state, the inner diameter of the insulativetube may increase, e.g., at longitudinal positions where the tube is notconstrained by the transition rings and expands into the electrode coil,as illustrated with respect to insulative tube 226 in FIGS. 6B and 7B.In some examples, in the expanded state, the inner diameter of theinsulative tube at a center of the insulative tube is greater than theinner diameter of the insulative tube at the tube distal end and thetube proximal end.

FIG. 8 is a flow diagram of an example technique for manufacturing acoil electrode assembly 100 to be attached to an implantable medicallead. The technique of FIG. 8 will be described with concurrentreference to coil electrode assembly 100 (FIGS. 2-5) having a first end134 (FIG. 3) and a second end 136 (FIG. 4), although a person havingordinary skill in the art will understand that the technique may beperformed in reference to an electrode assembly having a first end 200(FIGS. 6A and 6B) and a second end 240 (FIGS. 7A and 7B), anotherelectrode assembly, another implantable medical lead, or any othermedical device.

Method 200 of FIG. 8 includes attaching insulative tube 122 to secondtransition ring 126 (302). Insulative tube 122, with second transitionring 126 attached, is inserted within coil lumen 116 defined by windings114 of coil electrode 112 (304). Insulative tube 122 is attached tofirst transition ring 124 (306). In some examples, insulative tube 122is attached to first and second transition rings 124 and 126 withadhesive 146. Adhesive 146 can be applied along distal portion 140 andproximal portion 142 of the exterior surface of insulative tube 122.Adhesive 146 can also be applied to an exterior surface of insulativetube 122 before or after placement inside coil lumen 116. In someexamples, instead of applying adhesive 146 to insulative tube 122,adhesive 146 can be applied to an internal surface of first and secondtransition rings 124 and 126.

In some examples, the order of steps 302, 304, and 306 can be rearrangedwithout impacting the finished product (e.g., step 304 then steps 302and 306). Steps 302, 304, and 306 may need to be completed before thesteps welding and applying heat. For example, insulative tube 122 can beinserted into coil lumen 116 before attaching either first or secondtransition 124 and 126, e.g., switching steps 302 and 304. In someexamples, steps 306 and 302 may also be switched.

Once insulative tube 122 is within coil lumen 116 defined by coilelectrode 112 and first and second transition rings 124 and 126 areattached to insulative tube 122, coil electrode 122 is welded to firstand second transition rings 124 and 126 (308). Insulative tube 122 canthen be transitioned to the expanded state to partially embed coilelectrode 112 within insulative tube 122 (310). Insulative tube 122 canbe transitioned to the expanded state by application of heat and/or air(or other gas or liquid) pressure. The parameters of heat and/or airpressure may be selected to ensure insulative tube 122 does not ruptureor overflow, or is otherwise damaged. Applying pressure may includeapplying air or another fluid or gas to an inside of insulative tube 122over a range of between approximately 60 seconds to approximately 90seconds at less than approximately 6900 Pascal (Pa) of internalpressure. Applying heat may include applying heat to insulative tube122, e.g., the inside of the tube, over a range of between approximately60 seconds to approximately 90 seconds at about 180 degrees Celsius (°C.). In one example, heat is applied to insulative tube 122 slowly forapproximately 60 to 90 seconds at approximately 180° C., and internalpressure within insulative tube 122 is applied at a low pressure, suchas less than 6900 Pa. In some examples, the heat and pressure areapplied together and, more particularly, applied in the form of heatedgas, e.g., air, delivered at a desired pressure, e.g., via a nozzle.

In some examples, based on predicted applications of coil electrodeassembly 100 and material properties, different temperatures and/orpressures can be used to modify the expansion of insulative tube 122.After expanding insulative tube 122, an outer diameter of insulativetube 122 is less than an outer diameter of coil electrode 112. Thetemperature of insulative tube 122 is allowed to cool down afterexpansion. First and second transition rings 124 and 126 can be attachedto a high-voltage conductor that extends within insulative tube 122.After coil electrode assembly 100 is complete, coil electrode assembly100 can be attached to a lead, e.g., an implantable medical lead (312).

It should be understood that various aspects disclosed herein may becombined in different combinations than the combinations specificallypresented in the description and accompanying drawings. It should alsobe understood that, depending on the example, certain acts or events ofany of the processes or methods described herein may be performed in adifferent sequence, may be added, merged, or left out altogether (e.g.,all described acts or events may not be necessary to carry out thetechniques). In addition, while certain aspects of this disclosure aredescribed as being performed by a single module or unit for purposes ofclarity, it should be understood that the techniques of this disclosuremay be performed by a combination of units or modules associated with,for example, a medical device.

In addition, it should be noted that system described herein may not belimited to treatment of a human patient. In alternative examples, thesystem may be implemented in non-human patients, e.g., primates,canines, equines, pigs, and felines. These other animals may undergoclinical or research therapies that may benefit from the subject matterof this disclosure.

Various examples have been described. These and other examples arewithin the scope of the following claims.

What is claimed is:
 1. An implantable medical lead configured to becoupled to an implantable medical device, the implantable medical leadcomprising a coil electrode assembly, the coil electrode assemblycomprising: a coil electrode extending from an electrode proximal end toan electrode distal end, the coil electrode defining an electrode lumenfrom the electrode proximal end to the electrode distal end, and thecoil electrode comprising a plurality of windings; an insulative tubeextending from a tube proximal end to a tube distal end, the insulativetube extending within the electrode lumen such that the coil electrodeextends along an outer surface of the insulative tube, the coilelectrode partially embedded within the insulative tube when theinsulative tube is in an expanded state to maintain a spacing betweenthe windings; a first transition ring at the electrode distal end andthe tube distal end, wherein a portion of the first transition ring iswithin the electrode lumen, wherein the first transition ring defines afirst transition ring lumen, and wherein a distal portion of theinsulative tube including the tube distal end is within the firsttransition ring lumen; and a second transition ring at the electrodeproximal end and the tube proximal end, wherein a portion of the secondtransition ring is within the electrode lumen, wherein the secondtransition ring defines a second transition ring lumen, and wherein aproximal portion of the insulative tube including the tube proximal endis within the second transition ring lumen.
 2. The implantable medicallead of claim 1, further comprising an adhesive disposed on the distalportion of the insulative tube and the proximal portion of theinsulative tube, wherein the adhesive is configured to connect the firsttransition ring to the distal portion of the insulative tube and thesecond transition ring to the proximal portion of the insulative tube.3. The implantable medical lead of claim 2, wherein the adhesive isdisposed on the insulative tube only between a surface of the firsttransition ring and the distal portion of the insulative tube andbetween a surface of the second transition ring and the proximal portionof the insulative tube.
 4. The implantable medical lead of claim 2,wherein an outer surface of the coil electrode is substantially free ofadhesive.
 5. The implantable medical lead of claim 1, wherein each ofthe first and second transition rings is welded to the coil electrode.6. The implantable medical lead of claim 1, wherein the insulative tubecomprises a polymer and is configured to be transitioned to the expandedstate by application of heat and air pressure.
 7. The implantablemedical lead of claim 6, wherein the polymer comprises polyurethane. 8.The implantable medical lead of claim 6, wherein the polymer has adurometer hardness of at least 50 Shore D.
 9. The implantable medicallead of claim 1, wherein in a pre-expanded state, an inner diameter ofthe insulative tube is substantially constant from the tube distal endto the tube proximal end, and wherein in the expanded state, the innerdiameter of the insulative tube at a center of the insulative tube isgreater than the inner diameter of the insulative tube at the tubedistal end and the tube proximal end.
 10. A coil electrode assembly foran implantable medical lead configured to be coupled to an implantablemedical device, the coil electrode assembly comprising: a coil electrodeextending from an electrode proximal end to an electrode distal end, thecoil electrode defining an electrode lumen from the electrode proximalend to the electrode distal end, and the coil electrode comprising aplurality of windings; an insulative tube extending from a tube proximalend to a tube distal end, the insulative tube extending within theelectrode lumen such that the coil electrode extends along an outersurface of the insulative tube, the coil electrode partially embeddedwithin the insulative tube when the insulative tube is in an expandedstate to maintain a spacing between the windings; a first transitionring at the electrode distal end and the tube distal end, wherein aportion of the first transition ring is within the electrode lumen,wherein the first transition ring defines a first transition ring lumen,and wherein a distal portion of the insulative tube including the tubedistal end is within the first transition ring lumen; and a secondtransition ring at the electrode proximal end and the tube proximal end,wherein a portion of the second transition ring is within the electrodelumen, wherein the second transition ring defines a second transitionring lumen, and wherein a proximal portion of the insulative tubeincluding the tube proximal end is within the second transition ringlumen.